Regulation of rotary compressors



April I T. CLARK El'AL REGULATION OF ROTARY COMPRESSORS Filed April 28,1943 INYE/VTOFJ M law 1 20 Patented Apr. 16, 1946 REGULATION OF'ROTARYCOMPRESSQRS Thomas Clark andLeslie Richard Fellows, Coventry, England,assignors to Armstrong Siddeley Motors Limited, Coventry, England.

Application April 28, 1943, Serial-No. 4845920 In Great Britain November5, 19.42

signed compression ratio is reached.

Our main object is to provide improved con trol means for the spillvalve of a rotary compressor.

This and other objects and advantages of the invention will be betterunderstood if attention be directed to the following description, inwhich reference is made to the accompanying diagrammatic drawing thesingle figure of which is a fragmentary sectional elevation of amulti-stage compressor having a spill valve which is automaticallyregulated, according to the invention, dependently upon the absolutepressure ratio.

Broadly, in carrying out the invention, there is a means responsive tothe pressure of the compressor at one place, a means responsive to thepressure in the compressor at a later stage, a fluid pressure servodevice having a control valve which is worked by a lever, and a rodinterconnecting the lever and the means responsive to the pressure inthe compressor at the said later stage whilst the other means,responsive to the pressure of the compressor at the said one place, isconnected to the rod intermediate its ends; such that the spill valvewill be automatically regulated in the manner aforesaid.

In a preferred arrangement the servo means by which the fluid spillvalve is actuated is controlled by a pair of bellows devices responsive,

respectively, to the pressures at different points of the compressor,one of the said devices acting directly to control the servo means andthe other acting to vary the leverage at which the said one devicecontrols the servo means.

Referring now to the single figure of the drawing, this shows acompressor comprising a stationary casing I98 carrying sets of fixedblades IDI, and a rotor i512 carrying sets of rotating blades I03. Thespill valve is shown in the form of a throttle vavle HM disposed in apassage-way I05 communicating with the interior of the compressor, nearthe relatively-narrow outlet end thereof. The throttlevalve carries acrank I06 connected to a pistonrod llll to be actuated thereby.- 1

In the present instance a chamber I08 containing an: atmospheric capsuleor bellows'device H38 is in communication with a point near the intaketo the compressor by a pipe line I an, and a cham ber.:l Ida containinga plunger HI, or this also may. bea bellowsdevice, is connected to alater stage bycthe pipeline H2. The plunger is held against a stop H3 bya spring H4 and operates a. lever 1 i5 through aconnecting rod IIG. Thisrod is position-ed' bythe capsule I09 by means of alink II'I.v The leverlidwhich has a slot H3 inone end, whereit is" engaged by a pin on theend of the connecting'rod I I5, operates a piston valve H9 through alink I20 and is connected to the piston rod Iil'l of a. servo pistonI2I. Fluid pressure for the servo cylinder I22 can be supplied from areservoir I23 along a pipe line I24, while the passage I25 are forexhaust purposes.

When the compressor is stationary at sea level the capsule I09 takes upa position according to the pressure at the compressor intake, and theplunger I I i is held against its stop by the spring II4 which ofi'ers avery low spring load. As the rotor starts the pressure in the compressorincreases and theplunger III is depressed against the spring H4 andoperates the piston valve H9 of the servo motor. The servo piston I2lwill take up a position in direct proportion to the depression of theplunger l i I. At a predetermined depression of the plunger the servopiston will come to the end of its stroke, when the spill valve I 04 isfully closed.

If the pressure at the compressor intake is decreased the capsule IBQwill become extended and this in turn will move th pin of the connectingrod H6 along the slot H8 in the lever H5 in a direction to shorten theleverage between the rod I I6 and the piston valve H9. This has theeiiect of allowing the servo pistonlZI to move the same distance aspreviously but for a shorter movement of the piston valve I I9. But whenthe compressor again speeds up the pressure on the plunger MI isincreased and the latter is depressed and once again, at a smallerpredetermined depression of the plunger, the servo piston will come tothe end of its stroke.

Thus for any fixed ratio of pressure on the capsule I69 and plunger IIIthe servo piston I 2| will travel the full length of its stroke.

What we claim as our invention and desire to secure by Letters Patent ofthe United States is:

1. For a rotary compressor, a fluid spill valve disposed between itsends, a means responsive to the pressure of the compressor at one stage,a means responsive to the pressure in the compressor at a later stage, afluid-pressure servo deends, an axially-movable device responsive to thepressure of the compressor at an early stage, an axially-movable deviceresponsive to the pressure in the compressor at a later stage, saiddevices movable in directions substantially at right angles to oneanother, a fluid-pressure servo device for actuating said spill valve,said servo device having a control valve movable in a directionapproximately parallel to the direction of movement of said seconddevice, a lever for actuating said control valve, a rod having apin-and-slot connection with said lever, said rod connected to saidsecond device and being substantially parallelto the direction ofmovement thereof, and said rod being connected intermediate its ends tosaid first device, such that said spill valve will be fully open whenthe compressor is stationary and will gradually close as the compressorspeed increases, being fully closed when the designed compression ratiois reached.

3. In an axial-flow compressor, the combination of a fluid spill valvedisposed between its ends, an axially-movable device responsive to thepressure of the compressor at an early stage, an

axially-movable device responsive to the pressure in the compressor at alater stage, a fluid-pressure servo device for actuating said spillvalve, said servo device having a control valve, a. lever for actuatingsaid control valve, and a rod connected intermediate its ends to saidfirst device and connected at one end to said second device andconnected at its other end to said lever in such manner that operationof said second device will actuate said member while operation of saidfirst device will vary the leverage at which said rod acts on saidlever, whereby said spill valve will be fully open when the compressoris stationary and will gradually close as the compressor speedincreases, being fully closed when the designed compression ratio isreached.

4. In an axial-flow compressor, the combination of a fluid spill valvedisposed between its ends, and servo means for actuating said spillvalve whereby it will be fully open when the compressor is stationaryand will gradually close as the compressor speed increases, being fullyclosed when the designed compression ratio is reached, said servo meansbeing controlled by a pair of bellows devices responsive, respectively,to the pressures at different points 01' the compressor, one of saiddevices acting directly to control said servo means and the other ofsaid devices acting to vary the leverage at which said one devicecontrols said servo means.

THOMAS CLARK. LESLIE RICHARD FELLOWS.

